1. Technical Field
The present invention relates in general to valves for controlling fluid flow and, in particular, to an improved system, method and apparatus for a split gate valve having mechanically-isolated seal surfaces.
2. Description of the Related Art
Gate valves with split closure mechanisms offer very economical, low torque options for some valve applications. Due to the inherent need for the gates to “float” within the body cavity, however, they have limited effectiveness in abrasive (e.g., sandy) environments, and/or during fracturing well services. The clearance tolerances that are built into split closure designs to facilitate the float for a bidirectional seal ability serve to work against the needed function of excluding the hard particles found in abrasive and fracturing operations from entering the internal components of the valve design.
One type of gate valve design that is not reliant on flow line pressure to maintain contact between the gates and the valve seats both upstream and downstream simultaneously is known as a “wedge style” gate valve. This configuration has been utilized by the industry as a reliable style for lower pressure fracture service applications. In a wedge style gate valve, the ramping together of both gate segments creates the mechanical load needed to seal against the line pressures. This mechanical seal is beneficial in both the open and closed positions for reducing the ingress of fractured aggregates during well workovers. However, a negative effect of the “wedging” feature is the extremely high torque that is needed to open and close the valves. The high torque requirements limit wedge style gate valves to small valve sizes and line pressures. In addition, hydraulic force is required to actuate the valve since manual force is insufficient. Thus, an improved wedge style gate valve design that overcomes the limitations of previous designs would be desirable.